Acid-neutralizing lubricating oil compositions



ACill)-NEUTRALIIZINGv LUBRICATING OIL COMPOSITIONS James H. Walker, Richmond, Califi, assignor to California Research Corporation, San Francisco, Cfillfl, a corporation of Delaware No Drawing. Application July 13, 1955 Serial No. 521,887

7 Claims. (Cl. 252-33) tofore.

During the normal operation of internal combustion engines, the lubricating oil becomes acidic because of the organic acids and peroxides formed by the oxidation of the lubricatingoils during engine operation, and because of the formation of sulfuric acid as a combustion product of the fuel, particularly of high-sulfur fuels. The sulfuric acid finds its way into the crankcase along with blowby gases.

In an ettort to neutralize the eifects of these acidic components in internal combustion engines, a number of organic compounds are being incorporated in lubricating oil compositions. Among these organic compounds are detergents which are added to the oils primarily as dispersing agents. However, a portion of these detergents is incidentally used as a neutralizing agent for the acids. For example, calcium cetyl phenate is incorporated into a lubricating oil composition for its detergent and its acid-neutralizing properties. Rather than use relatively expensive organic compounds for neutralizing acids, it would be more practical to use less expensive materials (e.g., inorganic compounds).

A great stride in this direction was made by the development set forth in the Lindstrom and Woodruti U. S. Patent No. 2,676,925. The lubricating oil compositions therein having high acid-neutralizing characteristics are obtained by forming a mixture of a lubricating oil, an oil-soluble dispersant (e. g., a calcium petroleum sulfonate), a dihydric alcohol of less than 6 carbon atoms (e.g., ethylene glycol), and an inorganic polyvalent metal base (e.g., a metal oxide or hydroxide). This mixture is heated to remove dihydric alcohol, then filtered to remove undispersed polyvalent betal base. The lubricating oil compositions obtained by the use of this Lindstrom-Woodrufi process have base ratios ranging from 1.75 to 4.0.

Base ratios are defined as the mol ratios of the basic material (i. e., the metal oxide or hydroxide) to the dispersant (i. e., a sulfonate).

An improvement in the above-noted Lindstrom-Woodrufir' process is set forth in Stuart-Brashear U. S. patent application Serial No. 196,077, filed June27, 1952, now abandoned, wherein a filtering agent, that is, the combination of a low-molecular weight monobasic carboxylic acid (e. g., formic acid) and a low-molecular-weight alpha-hydroxy acid (e.g., glycolic acid), is incorporated in the lubricating oil composition prior to filtering to permit greater ease of filtration.

However, although large amounts of acidic materials in lubricating oil compositions are neutralized by the 2,865,857 Patented Dec. 23, 1958 use of lubricating oils prepared by the above processes, continued efforts are being made to incorporate still greater quantities of acid-neutraliznig components in lubricating oil compositions.

Therefore, it is a primary object of this invention to set forth a process of preparing lubricating oil compositions in which a larger amount of acids can be neutralized than heretofore possible, that is, forming lubricating oil compositions having base ratios in excess of 4.

This and other objects of this invention will be apparent from the ensuing description and the appended claims.

In accordance with the present invention, it has been discovered that lubricating oil compositions having base ratios in excess of 4 (i. e., greater than 4) are obtained by treating lubricating oil compositions having base ratios less than 4 with a dihydric alcohol solution of an alkaline earth metal oxide or hydroxide in the presence of a filtering agent.

The lubricating oil compositions of this invention are prepared by forming an admixture of a primary lubricating oil composition (that is, a lubricating oil composition having a base ratio less than 4), a solution (or dispersion) of an alkaline earth metal base substance in a dihydric alcohol formed by adding a metal oxide (or hydroxide) to a dihydric alcohol, and a filtering agent, heating said admixture to remove dihydric alcohol, then filtering to form a clear filterable lubricating oil composition.

In spite of all of the attempts which have been made to incorporate larger amounts of base materials in lubricating 'oil compositions by the Lindstrom-Woodrutf and Stuart-Brashear processes noted hereinabove, it has not been possible to obtain lubricating oil compositions having the high base ratios of compositions obtained by the present process. Contrary to all expectations, high base ratios of 7 and greater can be obtained by the process of the invention set forth herein. cating oil compositions herein are characterized as those which can neutralize larger amounts of acid components formed in engine oils than heretofore possible with previous lubricating oil compositions.

It would be expected that lubricating oil compositions having base ratios in excess of 4 could be prepared by adding larger amounts of metal oxides or hydroxides during the preparation of the primary lubricating oil composition noted hereinabove. However, as exemplified by Examples 1 and 2, hereinbelow, regardless of the amounts of metal oxides or hydroxides and dihydric alcohols present in the initial admixture, the base ratios of compositions thus prepared are normally less than 4.

Example 1.-Preparati0n of a lubricating oil composition having a base ratio less than-4 ture was heated to 390 F. at an absolute pressure of.

15 mm. of Hg to remove col. The undispers ed by filtration.

water and excess ethylene gly- (or unreacted) lime was removed The resulting lubricating oil composition contained a total of 4.5% calcium by weight, of which 1.13% calcium was frcm the calcium sulfonate. 'The base ratio of this lubricating oil composition had a value of 3.

Thus, the lubri- 3 Exizrizple 2.-A tt einptii preparation of high base ratio composition from lar e d'fn'b'iihts base material dh'd dihydric alcohol A mixture of 600 grams of a mineral oil solution of a calcium mahogany petroleum sulfonate (the oil solution having 1.70% calcium) and 600 grams of a California solvent-refined parafiin base oil having a viscosity of 480 SSU at 100 F. was heated to 300 F. in a reaction flask. A mixture consisting of 110 grams of calcium hydroxide, 37 grams of glycolic acid, 33 grams of formic acid, and i500 grams of ethylene glycol was then slowly added to the reaction flask at an absolute pressure of mm. of Hg during a period of 3 hours. During this period, glycoland water of reaction were removed continuously. When glycol was no longer being distilled from the mixture, the reaction mixture was heated to 400' F. at an absolute pressure of 50 mm. of Hg and filtered. Surprisingly, analysis showed that the filtered product contained a total of only 2.65% calcium, of which 0.67% was sulfonate calcium. The base ratio was only 2.96:1. The theoretical base ratio from the above amount of calcium hydroxide and glycol should have been 6:1.

The primary lubricating oil composition (that is, the initial lubricating 'oil composition having a base -ratio less than 4) is prepared according to the process set forth in patent application Serial No. 296,077, noted hereinabove, by whichprocess an alkaline earth metal base substance is dissolved (or dispersed) in a dihydric alcohol (e. g., ethylene glycol), which solution (or dispersion) is then incorporated into a lubricating oil containing an oil-soluble metal sulfonate (e. g., an alkaline earth metal petroleum sulfonate), and a filtering agent (e. g., a combination of glycolic acid and formic acid), after which the mixture is heated to remove dihydric alcohol, and filtered, forming a clear filterable lubricating oil composition.

Suitable lubricating oils useful in the composition of this invention include a wide variety of lubricating oils, such as oils which can be manufactured by solvent treating, acid treating, etc.; various crude oils, such as those which can be obtained by synthesis (e. g., the Fischer- Tropsch process). Lubricating oils also include those derived from coal products and those synthetic oils in which the components of the inventive process are soluble, e. g., alkylene polymers (such as polymers of propylene, butylene, etc., and mixtures thereof), alkylene oxide type polymers, dicarboxylic acid esters and liquid esters of acids of phosphorus. Synthetic oils of the alkylene oxide type polymer which may be used include those exemplified by alkylene oxide polymers (e. g., propylene oxide polymers) and derivatives, including alkylene oxide polymers prepared by polymerizing alkylene oxides (e. g., propylene oxide) in the presence of Water or alcohols, e. g., ethyl alcohol, and esters of alkylene oxide type polymers, e. g., acetylated propylene oxide polymers prepared by acetylating the propylene oxide polymers containing hydroxyl groups.

Synthetic oils of the dicarboxylic acid ester type include those which are prepared by esterifying such dicarboxylic acids as adipic acid, azelaic acid, suberic acid, sebacic acid, alkenyl succinic acid, fumaric acid, maleic acid, etc., with alcohols such as butyl alcohol, hexyl alcohol, Z-ethylhexyl alcohol, dodecyl alcohol, etc. Examples of dicarboxylic acid ester synthetic oils include dibutyl adipate, dihexyl adipate, di-2-ethylhexyl sebacate, di-n-hexyl fumarate polymer, etc.

Synthetic oils of the type of liquid esters of acids of phosphorus include the esters of phosphoric acid, e. g., tricresyl phosphate; the esters of phosphonic acid, e. g., diethyl ester of decane phosphonic acid, or other such esters as obtained by reacting alkyl phosphonyl chlorides with hydroxyl-containing compounds, such as phenols and aliphatic alcohols, and with olefin oxides such as propylene oxide.

The metal oxides or hydroxides used as initial reactants are the oxides or hydroxides of the alkaline earth metals.

4 Because of the greater acid-neutralizing characteristics of the resulting composition, calcium is the preferred metal.

The dihydric alcohols used in obtaining the lubricating oil composition of this invention are glycols containing less than 5 carbon atoms; in particular, these glycols include vicinal-alkane diols having less than 5 carbon atoms. Suitable dihydric alcohols include. for example, ethylene glycol, propane diol-1,2; butane diol-2. 3; butane diol-l,2; etc. Ethylene glycol is preferred, because thereby greater amounts of metal base "are incorporated in the lubricating oil compositions. In general, the use of a low molecular weight dihydric alcohol (e. g., ethylene glycol) results in obtaining a greater amount of the basic materials dispersed in the lubricating oil than the use of a higher molecular weight dihydric alcohol (e. g., propylene glycol), when both are used in the same amounts by weight.

It is preferred to select a dihydric alcohol in which the alkaline earth -metal oxides or hydroxides have the greatest solubility. In the formation of solutions of alkaline earth metal basic materials in glycols, it is beneficial to use certain ratios by weight of the dihydric alcohol to the alkaline earth metal oxide or hydroxide. These ratios may vary from about 50:1 to about 2:1, 30:1 to about 10:1 being preferred.

The filter agents herein consist of the combination of low molecular weight, non-hydroxy, monocarboxylic acids and low molecular weight alpha-hydroxy acids.

Low molecular Weight, no-n-hydroxy, monocarboxylic acids are those containing no more than 3 carbon atoms, as exemplified by formic acid and acetic acid. The alkaline earth metal salts (particularly the calcium salts) of these low molecular weight monocarboxylic acids can also be used; or mixtures of the acids and the salts.

Alpha-hydroxy acids include those having no more than 3 carbon atoms, as exemplified by glycolic acid and lactic acid. The alkaline earth metal salts (particularly the calcium salts) of these alpha-hydroxy acids can be used; or mixtures of the acids and the salts.

The non-hydro-xy, monocarboxylic acids can be present in the filter agent in amounts from about 35 mole percent to about mole percent. Optimum filtering conditions are obtained when the non-hydrcxy, monocarboxylic acids comprise about 50 mole percent to about 65 mole percent of the filter agents.

The amount of filtering agent used is dependent on the amount of alkaline earth metal oxides or hydroxides incorporated in the dihydric alcohol. The mole ratio of filtering agent (when added as free acid) to the alkaline earth metal incorporated in the oil (i. e., the alkaline earth metal from the oxide or hydroxide incorporated in the dihydric alcohol in the process herein) can vary from about 0.2 to about 0.5.

The alkaline earth metal base substances herein are obtained by dispersing alkaline earth metal oxides or hydroxides in dihydric alcohols. The alkaline earth metal oxide or hydroxide reactants herein are believed to combine with the dihydric alcohol (e. g., ethylene glycol), to form an alkaline earth metal base substance. Thus, as used herein, the terms alkaline earth metal base or alkaline earth metal base substance mean the products resulting from the reaction of alkaline earth metal oxides or hydroxides and dihydric alcohols. The base material further can be described as a glycoxide or a glycolated metal base. (The noted reaction is described in Industrial & Engineering Chemistry, vol. 8, No. 9, page 451.)

Alkaline earth metal sulfonates used in the preparation of the primary lubricating oil composition (i. e., the lubricating oil composition having a base ratio less than 4) include those derived from sulfonic acids containing the following hydrocarbon radicals: dodecane, hexadecane, eicosane, triacontane radicals; radicals derived from petroleum hydrocarbons, such as white oil, wax, olefin polymers (e. g., polypropylene and polybutylene, etc.). The sulfonic acids used in preparing the sulfonates of this invention also include the oil-soluble sulfonic acids obtained from petroleum, such as the mahogany" acids, and the synthetic sulfonic acids prepared by various methods of synthesis (e. g., sulfonic acids prepared by reacting a chlorinated white oil With ben zene, using hydrofluoric acid as the catalyst, then treating the resulting white oil alkylated benzene with chlorosulfonic acid or fuming sulfuric acid to form a white oil benzene sulfonic acid).

Alkaline earth metal sulfonates are exemplified as follows: calcium white oil benzene sulfonate, magnesium white oil benzene sulfonate, calcium dipolypropene benzene sulfonate, magnesium dipolypropene benzene sulfonate, calcium mahogany petroleum sulfonate, magnesium mahogany petroleum sulfonate, calcium mahogany petroleum sulfo-nate, magnesium mahogany petroleum sulfonate, calcium triacontyl sulfonate, magnesium triacontyl sulfonate, calcium lauryl sulfonate, magnesium lauryl sulfonate, etc.

The sulfonates can be used in amounts of about 0.1% to 10%, by weight, of said finished composition. However, it is preferred to use from about 0.3% to about 2.0%, by weight, because lubricating oil compositions containing these amounts markedly improve the over-all rating of an engine. Expressed in millimols per kilogram of final lubricating oil composition, the sulfonates can be used in amounts of about 1 millimol per kilogram to about 110 millimols per kilogram, with a preferred range of about 3 millimols per kilogram to about millimols per kilogram.

The metal of the sulfonate may be the same as the metal of the basic material dispersed; or the metal of the sulfonate may be different from the metalof the basic material dispersed. For example, a calcium sulfonate may be used in a lubricating oil composition to stabilize a dispersion of a barium basic material, or a calcium sulfonate may be used in a lubricating oil composition to stabilize a dispersion of a calcium basic material.

Lubricating oil compositions having base ratios in excess of 4.0 are obtained in accordance with this invention by forming an admixture of a lubricating oil composition containing a metal sulfonate and having a base ratio less than 4.0, an alkaline earth metal oxide or hydroxide, a dihydric alcohol, and a filtering agent; heating said admixture to a temperature from about 175 F. to about 400 F. (250 F. to 350 F. being preferred) for a period of time sufficient to essentially complete the dispersion of metal basic material in the lubricating oil composition and to remove substantially all of the free unreacted dihydric alcohol, after which the mixture is filtered to remove any apparently undispersed (or unreacted) metal oxide or hydroxide. It is preferred to heat the lubricating oil compositions in the above-noted temperature ranges at reduced pressures, preferably at absolute pressures less than 150 mm. of Hg.

The following examples illustrate the preparation of lubricating oil compositions having base ratios in excess Example 3.Preparati0n- 0 a lubricating oil composition having a base ratio in excess of 4 A mixture consisting of 252 grams of a lubricating oil composition containing a calcium petroleum sulfonate and having a base ratio of 2.8:1 (which composition contained a total of 4.5% calcium), and 58.9 grams of a California solvent-refined paraiiin base oil having a viscosity of 480 SSU at 100 F., was added to a solution of 25.5 grams of calcium hydroxide in 114 grams of ethylene glycol. To this mixture was further added (at room temperature) a filtering agent consisting of 10 grams of glycolic acid and 6.75 grams of formic acid.

The whole mixture w'as'heated to a maximum temperature of 390 F. at an absolute pressure of 50 mm. of Hg. to remove water and unreacted ethylene glycol.

After filtration, the-lubricating oil composition contained a total of 5.50% calcium, by weight, of which 0.81% by weight was the calcium from the sulfonate. The base ratio of this lubricating oil composition had a value of 5.83.

Example 4.Preparati0n of lubricating oil composition having a base ratio of 7.15

A mixture of 252 grams of the reaction product of Example 3 and 58.9 grams of a California solvent-refined parafiin base lubricating oil having a viscosity of 480 SSU at l00 F. was added to a solution of 225 grams of calcium hydroxide in 114 grams of ethylene glycol at room temperature, after which was added a filtering agent consisting of 10 grams of glycolic acid and 6.75 grams of formic acid. The whole mixture was heated to a maximum of 390 F. at an absolute pressure of 50 mm. of Hg to remove water and excess unreacted ethylene glycol. The filtered lubricating oil composition contained a total calcium content of 4.96%, by weight, of which 0.61% was from neutral calcium sulfonate. Thus,

the base ratio of this lubricating oil composition was 252 grams of a mineral oil solution of a calcium sulfonate (the oil solution containing 3.34% calcium and having a base ratio of about 2.8) was diluted with 59 grams of a California solvent-refined paraflin base oil having a viscosity of 480 SSU at F. To this mineral oil solution of 22.5 grams of calcium hydroxide in 114 grams of ethylene, glycol at room temperature, after which there was added a filter agent consisting of 10 grams of glycolic acid and 6.75 grams of formic acid. The Whole mixture was heated to a maximum temperature of 390 F. at an absolute pressure of 50 mm. of Hg to remove water and unreacted ethylene glycol. The filtered reaction product contained a total of 5.11% calcium, by weight, of which 0.65% by weight was calcium from neutral calcium sulfonate. The base ratio of this reaction product was 6.85:1.

Numerous variations of the methods presented here may be employed in preparing the lubricating oil compositions of this invention. For example, the metal oxides or hydroxides may be blended with the sulfonate in the lubricating oil prior to being mixed with the dihydric alcohol, or the dihydric alcohol and the sulfonate may be blended together first, or all of the ingredients may be blended together at once. However, it is preferred to mix the dihydric alcohols and the metal oxides or hydroxides first to obtain the colloidal dispersion or dissolution of the metal oxides or hydroxides in the dihydric alcohol before mixing with lubricating oil and sulfonate.

In addition to the components set forth hereinabove, the lubricating oil compositions prepared by the process of this invention may contain other groups of additives; for example, oxidation inhibitors, such as organo esters of phosphorus (e. g., zinc cetylphenyl dithiophosphate and calcium cetylphenyl dithiophosphate); metal salts of thiocarbamic acids (e. g., zinc dibutyl dithiocarbamate); sulfides (e. g., sulfurized diparaffin sulfide, sulfurized olefins, etc.); amines (phenyl alpha naphthylamine, 1,4-diamino (dodecyl) .anthraquinone, etc.).

Furthermore, the lubricating oil compositions herein may contain pour point depressants, corrosion inhibitors, oiliness agents, extreme pressure agents, blooming agents,

compounds for enhancing the viscosity index of hydro- 1. The process of forming stable, filterable lubricating oil compositions having base ratios in excess of 4, comprising forming an admixture. consisting of a dihydric alcohol having less than carbon atoms, an inorganic substance selected from the group consisting of alkaline earth metal oxides and hydroxides, a filter agent, a lubricating oil, and from 0.3% to 2%, by weight, of an alkaline earth metal 'sulfonate, heating said admixture to a temperature in the range of about 250 E. to about 350 F. for a time sufficient to remove free dihydric alcohol, followed by filtration, and incorporating in the resulting filtrate a dihydric alcohol having less than 5 carbon atoms, an inorganic substance selected from the group consisting of alkaline earth metal oxides and bydroxides, a lubricating oil, from 03% to 2%, by weight, of an alkaline earth metal sulfonate, and a filter agent, heating the whole mixture to a temperature in the range of about 250 F. to about 350 F. for a period of time sufficient to remove free dihydric alcohol, followed by filtration, wherein said filter agent is a combination of glycolic acid and formic acid such that the glycolic acid is present in amounts of about mol percent to about 80 mol percent in the glycolic acid-formic ac i d combination, said filter agent being present in amounts such that the mol ratio of said filter agent to said inorganic substance has a value from about 0.2 to about 0.5, and wherein the Weight ratio of dihydric alcohol to said inorganic substance is from 30:1 to 10:1.

2. The process of forming stable, filterable lubricating oil compositions having base ratios in excess of 4, comprising forming an admixture consisting of a dihydric alcohol having less than 5 carbon atoms, an inorganic substance .selected from the group consisting of alkaline earth metal oxides and hydroxides, a filter agent, a lubricating oil, and from 0.01% to 10%, by weight, of an alkaline earth metal sulfonate, heating said admixture to a temperature in the range of about 250 F. to about 350 F. for atirne sufficient to remove free dihydric alcohol, followed by filtration, and incorporating in the resulting filtrate a dihydric alcohol having less than 5 carbon atoms, an inorganic substance selected from the group consisting of alkaline earth metal oxides and hydroxides, a lubricating oil, from 0.01% to 10%, by weight, of an alkaline earth metal sulfonate, and a filter agent, heatingthe whole mixture to a temperature in the range of about 250 F. to about 350 F. for a period of time sufficient to remove free dihydric alcohol, followed by filtration, wherein said filter agent is a combination of glycolic acid and formic acid such that the glycolic acid is present in amounts of about mol percent to about mol percent in the glycolic acid-formic acid combination, said filter agent being present in amounts such that the mol ratio of said filter agent to said inorganic substance has a value from about 0.2 to about 0.5, and wherein the weight ratio of said dihydric alcohol to said inorganic substance is from 30:1 to 10: l. i

3. The process of forming stable, filterable lubricating oil compositions having base ratios in excess of 4, comprising first forming an admixture of ethylene glycol, an inorganic substance selected from the group consisting of calcium oxide and hydroxide, a filter agent, from 0.3% to 2%, by weight, of an alkaline earth metal sulfonate, and a lubricating oil, heating said admixture to a temperaturein the range of about 250 F. to about 350 F. for a time sufificient to remove free ethylene glycol, followed by filtration, and incorporating in the resulting filtrate a lubricating oil, ethylene glycol, an inorganic substance selected'zfrom the group consisting of calcium oxide and hydroxide, a filter agent, and from 0.3% to 2%, by weight, 'of an alkaline earth metal sulfonate, heating the whole mixture to a temperature in the range of about 250 F. to about 350 F. for a period of time suificient to remove free ethylene glycol, followed by filtration, wherein said filter agent is a combination of glycolic acid and formic acid such that the glycolic acid is present in amounts of about 35 mol percent to about mol percent in the glycolic acid-formic acid combination, said filter agent being present in an amount such that the mol ratio of said filter agent to said inorganic substance has a value of about 0.2 to about 0.5, and wherein said inorganic substance is present in an amount such that the ethylene glycol-inorganic substance weight ratio has a value from about 30:1 to 10:1.

4. The process of claim 3, wherein said lubricating oil is a petroleum mineral lubricating oil.

5 The process of claim 3, wherein said lubricating oil is an oil of lubricating viscosity, and said sulfonate is a calcium petroleum mahogany sulfonate.

6. The process of claim 3, wherein said filter agent is a combination of calcium glycolate and calcium formate.

7. The process of claim 3, wherein said inorganic substance is calcium hydroxide.

References Cited in the file of this patent UNITED STATES PATENTS 2,671,758 Vinograd et al. Mar. 9, 1954 2,676,925 Lindstrom et al. Apr. 27, 1954 2,716,087 Woodrufi et al Aug. 23, 1955 UNITED STATES PATENT OFFICE CERTIFlfiAl-E 0F 'CORECTION December 23, 1958 Patent No a 2,865 857 James H Walker It is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 54, for "betal. read metal line 64. for Serial No. 196,077" read Serial No, 296,077 =0 Signed and sealed this 14th day of April 1959.,

(SEAL) Attest:

KARL H, AXLINE Attesting Officer 7 ROBERT C. WATSON Commissioner of Patents 

1. THE PROCESS OF FROMING STABLE, FILTERABLE LUBRICATING OIL COMPOSITIONS HAVING BASE RATIOS IN EXCESS OF 4, COMPRISING FORMING AN ADMIXTURE CONSISTING OF A DIHYDRIC ALCOHOL HAVING LESS THAN 5 CARBON ATOMS, AN INORGANIC SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF ALKALINE EARTH METAL OXIDES AND HYDROXIDES, A FILTER AGENT, A LUBRICATING OIL, AND FROM 0.3% TO 2%, BY WEIGHT, OF AN ALKALINE EARTH METAL SULFONATE, HEATING SAID ADMIXTURE TO A TEMPERATURE IN THE RANGE OF ABOUT 250*F. TO ABOUT 350*F. FOR A TIME SUFFICIENT TO REMOVE FREE DIHYDRIC ALCOHOL, FOLLOWED BY FILTRATION, AND INCORPORATING IN THE RESULTING FILTRATE A DIHYDRIC ALCOHOL HAVING LESS THAN 5 CARBON ATOMS, AN INORGANIC SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF ALKALINE EARTH METAL OXIDES AND HYDROXIDES, A LUBRICATING OIL, FROM 0.3% TO 2%, BY WEIGHT, OF AN ALKALINE EARTH METAL SULFONATE, AND A FILTER AGENT, HEATING THE WHOLE MIXTURE TO A TEMPERATURE IN THE RANGE OF ABOUT 250*F. TO ABOUT 350*F. FOR A PERIOD OF TIME SUFFICIENT TO REMOVE FREE DIHYDRIC ALCOHOL, FOLLOWED BY FILTRATION, WHEREIN SAID FILTER AGENT IS A COMBINATION OF GLYCOLIC ACID AND FORMIC ACID SUCH THAT THE GLYCOLIC ACID IS PRESENT IN AMOUNTS OF ABOUT 35 MOL PERCENT TO ABOUT 80 MOL PERCENT IN THE GLYCOLIC ACID-FORMIC ACID COMBINATION, SAID FILTER AGENT BEING PRESENT IN ABOUTNS SUCH THAT THE MOL RATIO OF SAID FILTER AGENT TO SAID INORGANIC SUBSTANCE HAS A VALUE FROM ABOUT 0.2 TO ABOUT 0.5, AND WHEREIN THE WEIGHT RATIO OF DIHYDRIC ALCOHOL TO SAID INORGANIC SUBSTANCE IS FROM 30:1 TO 10:1. 